The present invention relates to acoustic wave communications and more particularly to an improved electronic system and technique for telemetering underwater depth and descent rate data via an acoustic frequency link.
In the field of underwater telemetry, free-falling hydrographic packages are commonly employed to retrieve and transmit research data pertinent to the nature of an underwater environment. Generally designed to descend in the water at a fixed and stable rate for optimum information retrieval, these hydrographic packages are typically provided with pressure transducers that produce signals indicative of the package's underwater depth for correlation with the research data being retrieved. The underwater depth and descent rate of the hydrographic packages, as signaled by the pressure transducers, are vital to the effective mapping of the retrieved information and must be continuously and accurately monitored throughout the descent of the packages without disrupting their stabilized free-fall through the water.
Various acoustic wave communication systems and associated techniques have been devised and developed to relay sensor data through water for remote measuring and analyzation. However, while such communication systems and techniques have been generally successful in acoustically projecting data underwater, they have not been sufficiently accurate in underwater telemetry operations involving moving acoustical projectors, such as the free-falling hydrographic packages, due to errors induced by the Doppler effect. In addition, existing acoustic wave communication systems have not been easily adapted to present hydrographic operations, generally requiring interfacing that has interfered with the performance of the hydrographic packages and adversely affected stabilization of their free-fall descent.